2 files changed, 377 insertions, 0 deletions
diff --git a/tests/Jellyfin.Server.Implementations.Tests/Item/AlternateVersionQueryTranslationTests.cs b/tests/Jellyfin.Server.Implementations.Tests/Item/AlternateVersionQueryTranslationTests.cs
new file mode 100644
index 0000000000..c8aa14af58
--- /dev/null
+++ b/tests/Jellyfin.Server.Implementations.Tests/Item/AlternateVersionQueryTranslationTests.cs
@@ -0,0 +1,233 @@
+#pragma warning disable RS0030 // Do not use banned APIs: Guid == is required inside EF expression trees to mirror the production query shapes.
+
+using System;
+using System.Linq;
+using Jellyfin.Database.Implementations;
+using Jellyfin.Database.Implementations.Entities;
+using Jellyfin.Database.Implementations.Locking;
+using Jellyfin.Database.Providers.Sqlite;
+using Microsoft.Data.Sqlite;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Logging.Abstractions;
+using Xunit;
+
+namespace Jellyfin.Server.Implementations.Tests.Item;
+
+/// <summary>
+/// Verifies that the alternate-version-aware query shapes used by the resume filter
+/// (BaseItemRepository.TranslateQuery) and the DatePlayed ordering (OrderMapper) translate
+/// and evaluate correctly on the SQLite provider.
+/// </summary>
+public sealed class AlternateVersionQueryTranslationTests : IDisposable
+{
+    private readonly SqliteConnection _connection;
+    private readonly DbContextOptions<JellyfinDbContext> _dbOptions;
+
+    public AlternateVersionQueryTranslationTests()
+    {
+        _connection = new SqliteConnection("Data Source=:memory:");
+        _connection.Open();
+
+        _dbOptions = new DbContextOptionsBuilder<JellyfinDbContext>()
+            .UseSqlite(_connection)
+            .Options;
+
+        using var ctx = CreateDbContext();
+        ctx.Database.EnsureCreated();
+    }
+
+    [Fact]
+    public void ResumeFilter_VersionProgress_SurfacesPlayedVersion()
+    {
+        Guid userId, primaryId, versionId, otherId;
+
+        using (var ctx = CreateDbContext())
+        {
+            (userId, primaryId, versionId, otherId) = Seed(ctx);
+        }
+
+        using (var ctx = CreateDbContext())
+        {
+            var inProgress = ctx.UserData
+                .Where(ud => ud.UserId == userId && ud.PlaybackPositionTicks > 0);
+
+            // Scope to the seeded items; EnsureCreated also seeds a placeholder row.
+            var seededIds = new[] { primaryId, versionId, otherId };
+
+            // Mirrors the resumable=true filter in BaseItemRepository.TranslateQuery.
+            var inProgressIds = inProgress.Select(ud => ud.ItemId);
+            var resumable = ctx.BaseItems
+                .Where(e => seededIds.Contains(e.Id))
+                .Where(e => inProgressIds.Contains(e.Id))
+                .Where(e => !ctx.BaseItems
+                    .Where(s => s.Id != e.Id && (s.PrimaryVersionId ?? s.Id) == (e.PrimaryVersionId ?? e.Id))
+                    .Any(s =>
+                        inProgress.Where(su => su.ItemId == s.Id).Max(su => su.LastPlayedDate)
+                            > inProgress.Where(eu => eu.ItemId == e.Id).Max(eu => eu.LastPlayedDate)
+                        || (inProgress.Where(su => su.ItemId == s.Id).Max(su => su.LastPlayedDate)
+                                == inProgress.Where(eu => eu.ItemId == e.Id).Max(eu => eu.LastPlayedDate)
+                            && s.Id.CompareTo(e.Id) < 0)))
+                .Select(e => e.Id)
+                .ToList();
+
+            Assert.Equal([versionId], resumable);
+
+            // The not-resumable direction keeps primaries only.
+            var resumableMovieIds = inProgress
+                .Join(ctx.BaseItems, ud => ud.ItemId, bi => bi.Id, (ud, bi) => bi.PrimaryVersionId ?? bi.Id);
+            var notResumable = ctx.BaseItems
+                .Where(e => seededIds.Contains(e.Id) && e.PrimaryVersionId == null)
+                .Where(e => !resumableMovieIds.Contains(e.Id))
+                .Select(e => e.Id)
+                .ToList();
+
+            Assert.Equal([otherId], notResumable);
+        }
+    }
+
+    [Fact]
+    public void ResumeFilter_TiedLastPlayedDate_KeepsSingleVersion()
+    {
+        Guid userId, primaryId, versionAId, versionBId;
+
+        using (var ctx = CreateDbContext())
+        {
+            (userId, primaryId, versionAId, versionBId) = SeedTiedVersions(ctx);
+        }
+
+        using (var ctx = CreateDbContext())
+        {
+            var inProgress = ctx.UserData
+                .Where(ud => ud.UserId == userId && ud.PlaybackPositionTicks > 0);
+
+            var seededIds = new[] { primaryId, versionAId, versionBId };
+            var inProgressIds = inProgress.Select(ud => ud.ItemId);
+
+            // The exact production dedup, including the Guid.CompareTo tie-break. This asserts the
+            // expression translates on SQLite and that two versions sharing an identical LastPlayedDate
+            // collapse to a single row instead of double-listing the item in Continue Watching.
+            var resumable = ctx.BaseItems
+                .Where(e => seededIds.Contains(e.Id))
+                .Where(e => inProgressIds.Contains(e.Id))
+                .Where(e => !ctx.BaseItems
+                    .Where(s => s.Id != e.Id && (s.PrimaryVersionId ?? s.Id) == (e.PrimaryVersionId ?? e.Id))
+                    .Any(s =>
+                        inProgress.Where(su => su.ItemId == s.Id).Max(su => su.LastPlayedDate)
+                            > inProgress.Where(eu => eu.ItemId == e.Id).Max(eu => eu.LastPlayedDate)
+                        || (inProgress.Where(su => su.ItemId == s.Id).Max(su => su.LastPlayedDate)
+                                == inProgress.Where(eu => eu.ItemId == e.Id).Max(eu => eu.LastPlayedDate)
+                            && s.Id.CompareTo(e.Id) < 0)))
+                .Select(e => e.Id)
+                .ToList();
+
+            var survivor = Assert.Single(resumable);
+            Assert.Contains(survivor, new[] { versionAId, versionBId });
+        }
+    }
+
+    [Fact]
+    public void DatePlayedOrdering_VersionProgress_SortsPrimaryByVersionDate()
+    {
+        Guid userId, primaryId, otherId;
+
+        using (var ctx = CreateDbContext())
+        {
+            (userId, primaryId, _, otherId) = Seed(ctx);
+        }
+
+        using (var ctx = CreateDbContext())
+        {
+            // Scope to the seeded items; EnsureCreated also seeds a placeholder row.
+            var seededIds = new[] { primaryId, otherId };
+
+            // Mirrors the DatePlayed mapping in OrderMapper.
+            var ordered = ctx.BaseItems
+                .Where(e => seededIds.Contains(e.Id) && e.PrimaryVersionId == null)
+                .OrderByDescending(e => ctx.UserData
+                    .Where(w => w.UserId == userId && (w.ItemId == e.Id || w.Item!.PrimaryVersionId == e.Id))
+                    .Max(f => f.LastPlayedDate))
+                .Select(e => e.Id)
+                .ToList();
+
+            // The movie whose only progress is on its alternate version sorts before the unplayed one.
+            Assert.Equal([primaryId, otherId], ordered);
+        }
+    }
+
+    private static (Guid UserId, Guid PrimaryId, Guid VersionId, Guid OtherId) Seed(JellyfinDbContext ctx)
+    {
+        var user = new User("test", "auth-provider", "reset-provider");
+        ctx.Users.Add(user);
+
+        var primary = new BaseItemEntity { Id = Guid.NewGuid(), Type = "MediaBrowser.Controller.Entities.Movies.Movie" };
+        var version = new BaseItemEntity { Id = Guid.NewGuid(), Type = "MediaBrowser.Controller.Entities.Movies.Movie", PrimaryVersionId = primary.Id };
+        var other = new BaseItemEntity { Id = Guid.NewGuid(), Type = "MediaBrowser.Controller.Entities.Movies.Movie" };
+        ctx.BaseItems.AddRange(primary, version, other);
+
+        // Progress only on the alternate version.
+        ctx.UserData.Add(new UserData
+        {
+            ItemId = version.Id,
+            Item = version,
+            UserId = user.Id,
+            User = user,
+            CustomDataKey = version.Id.ToString("N"),
+            PlaybackPositionTicks = 1000,
+            LastPlayedDate = new DateTime(2026, 1, 2, 0, 0, 0, DateTimeKind.Utc)
+        });
+
+        ctx.SaveChanges();
+        return (user.Id, primary.Id, version.Id, other.Id);
+    }
+
+    private static (Guid UserId, Guid PrimaryId, Guid VersionAId, Guid VersionBId) SeedTiedVersions(JellyfinDbContext ctx)
+    {
+        var user = new User("test", "auth-provider", "reset-provider");
+        ctx.Users.Add(user);
+
+        var primary = new BaseItemEntity { Id = Guid.NewGuid(), Type = "MediaBrowser.Controller.Entities.Movies.Movie" };
+        var versionA = new BaseItemEntity { Id = Guid.NewGuid(), Type = "MediaBrowser.Controller.Entities.Movies.Movie", PrimaryVersionId = primary.Id };
+        var versionB = new BaseItemEntity { Id = Guid.NewGuid(), Type = "MediaBrowser.Controller.Entities.Movies.Movie", PrimaryVersionId = primary.Id };
+        ctx.BaseItems.AddRange(primary, versionA, versionB);
+
+        // Both versions in progress with the exact same LastPlayedDate - the tie that a strict '>' cannot break.
+        var tied = new DateTime(2026, 1, 2, 0, 0, 0, DateTimeKind.Utc);
+        ctx.UserData.Add(new UserData
+        {
+            ItemId = versionA.Id,
+            Item = versionA,
+            UserId = user.Id,
+            User = user,
+            CustomDataKey = versionA.Id.ToString("N"),
+            PlaybackPositionTicks = 1000,
+            LastPlayedDate = tied
+        });
+        ctx.UserData.Add(new UserData
+        {
+            ItemId = versionB.Id,
+            Item = versionB,
+            UserId = user.Id,
+            User = user,
+            CustomDataKey = versionB.Id.ToString("N"),
+            PlaybackPositionTicks = 2000,
+            LastPlayedDate = tied
+        });
+
+        ctx.SaveChanges();
+        return (user.Id, primary.Id, versionA.Id, versionB.Id);
+    }
+
+    private JellyfinDbContext CreateDbContext()
+    {
+        return new JellyfinDbContext(
+            _dbOptions,
+            NullLogger<JellyfinDbContext>.Instance,
+            new SqliteDatabaseProvider(null!, NullLogger<SqliteDatabaseProvider>.Instance),
+            new NoLockBehavior(NullLogger<NoLockBehavior>.Instance));
+    }
+
+    public void Dispose()
+    {
+        _connection.Dispose();
+    }
+}
diff --git a/tests/Jellyfin.Server.Implementations.Tests/Item/BaseItemRepositoryGroupingTests.cs b/tests/Jellyfin.Server.Implementations.Tests/Item/BaseItemRepositoryGroupingTests.cs
new file mode 100644
index 0000000000..083f725db9
--- /dev/null
+++ b/tests/Jellyfin.Server.Implementations.Tests/Item/BaseItemRepositoryGroupingTests.cs
@@ -0,0 +1,144 @@
+using System;
+using System.Linq;
+using Emby.Server.Implementations.Data;
+using Jellyfin.Database.Implementations;
+using Jellyfin.Database.Implementations.Entities;
+using Jellyfin.Database.Implementations.Locking;
+using Jellyfin.Database.Providers.Sqlite;
+using Jellyfin.Server.Implementations.Item;
+using MediaBrowser.Controller;
+using MediaBrowser.Controller.Configuration;
+using MediaBrowser.Controller.Entities;
+using MediaBrowser.Model.Configuration;
+using MediaBrowser.Model.Entities;
+using Microsoft.Data.Sqlite;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Logging.Abstractions;
+using Moq;
+using Xunit;
+using BaseItemKind = Jellyfin.Data.Enums.BaseItemKind;
+
+namespace Jellyfin.Server.Implementations.Tests.Item;
+
+public sealed class BaseItemRepositoryGroupingTests : IDisposable
+{
+    private readonly SqliteConnection _connection;
+    private readonly DbContextOptions<JellyfinDbContext> _dbOptions;
+    private readonly BaseItemRepository _repository;
+    private readonly string _movieTypeName;
+
+    public BaseItemRepositoryGroupingTests()
+    {
+        _connection = new SqliteConnection("Data Source=:memory:");
+        _connection.Open();
+
+        _dbOptions = new DbContextOptionsBuilder<JellyfinDbContext>()
+            .UseSqlite(_connection)
+            .Options;
+
+        using (var ctx = CreateDbContext())
+        {
+            ctx.Database.EnsureCreated();
+        }
+
+        var factory = new Mock<IDbContextFactory<JellyfinDbContext>>();
+        factory.Setup(f => f.CreateDbContext()).Returns(CreateDbContext);
+
+        var itemTypeLookup = new ItemTypeLookup();
+        _movieTypeName = itemTypeLookup.BaseItemKindNames[BaseItemKind.Movie];
+
+        var serverConfigurationManager = new Mock<IServerConfigurationManager>();
+        serverConfigurationManager.Setup(c => c.Configuration).Returns(new ServerConfiguration());
+
+        _repository = new BaseItemRepository(
+            factory.Object,
+            new Mock<IServerApplicationHost>().Object,
+            itemTypeLookup,
+            serverConfigurationManager.Object,
+            NullLogger<BaseItemRepository>.Instance);
+    }
+
+    public void Dispose()
+    {
+        _connection.Dispose();
+    }
+
+    [Fact]
+    public void GetItemList_VersionGroup_ReturnsPrimaryVersion()
+    {
+        // The alternate version sorts before the primary by id, so a plain Min(Id) per
+        // presentation key would wrongly pick the alternate as the group representative.
+        var primaryId = Guid.Parse("eeeeeeee-eeee-eeee-eeee-eeeeeeeeeeee");
+        var alternateId = Guid.Parse("11111111-1111-1111-1111-111111111111");
+        var presentationKey = primaryId.ToString("N");
+
+        using (var ctx = CreateDbContext())
+        {
+            ctx.BaseItems.Add(CreateMovieEntity(primaryId, "Movie", presentationKey, null));
+            ctx.BaseItems.Add(CreateMovieEntity(alternateId, "Movie - 1080p", presentationKey, primaryId));
+            ctx.SaveChanges();
+        }
+
+        var result = _repository.GetItemList(CreateQuery());
+
+        var item = Assert.Single(result);
+        Assert.Equal(primaryId, item.Id);
+    }
+
+    [Fact]
+    public void GetItemList_GroupWithoutPrimary_FallsBackToMinId()
+    {
+        var firstId = Guid.Parse("22222222-2222-2222-2222-222222222222");
+        var secondId = Guid.Parse("dddddddd-dddd-dddd-dddd-dddddddddddd");
+        var otherPrimaryId = Guid.Parse("cccccccc-cccc-cccc-cccc-cccccccccccc");
+        var presentationKey = otherPrimaryId.ToString("N");
+
+        using (var ctx = CreateDbContext())
+        {
+            ctx.BaseItems.Add(CreateMovieEntity(firstId, "Movie", presentationKey, otherPrimaryId));
+            ctx.BaseItems.Add(CreateMovieEntity(secondId, "Movie - 4K", presentationKey, otherPrimaryId));
+            ctx.SaveChanges();
+        }
+
+        var result = _repository.GetItemList(CreateQuery());
+
+        var item = Assert.Single(result);
+        Assert.Equal(firstId, item.Id);
+    }
+
+    private static InternalItemsQuery CreateQuery()
+    {
+        // IncludeOwnedItems keeps the alternate version rows in the query so the
+        // grouping collapse is what picks the group representative.
+        return new InternalItemsQuery(new Database.Implementations.Entities.User("test", "auth", "reset"))
+        {
+            IncludeItemTypes = [BaseItemKind.Movie],
+            IncludeOwnedItems = true
+        };
+    }
+
+    private BaseItemEntity CreateMovieEntity(Guid id, string name, string presentationKey, Guid? primaryVersionId)
+    {
+        return new BaseItemEntity
+        {
+            Id = id,
+            Type = _movieTypeName,
+            Name = name,
+            PresentationUniqueKey = presentationKey,
+            PrimaryVersionId = primaryVersionId,
+            MediaType = "Video",
+            IsMovie = true,
+            IsFolder = false,
+            IsVirtualItem = false
+        };
+    }
+
+    private JellyfinDbContext CreateDbContext()
+    {
+        return new JellyfinDbContext(
+            _dbOptions,
+            NullLogger<JellyfinDbContext>.Instance,
+            new SqliteDatabaseProvider(null!, NullLogger<SqliteDatabaseProvider>.Instance),
+            new NoLockBehavior(NullLogger<NoLockBehavior>.Instance));
+    }
+}